Reference is made to commonly-assigned U.S. Ser. No. 09/941,009 filed herewith, entitled xe2x80x9cElectroluminescent Devices Having Diarylanthracene Ladder Polymers in Emissive Layersxe2x80x9d by Zheng et al the disclosure of which is incorporated herein.
The present invention relates to electroluminescent (EL) devices having diarylanthracene polymers.
Electroluminescent (EL) devices such as light emitting diode (LED) are opto-electronic devices which radiate light on the application of an electrical field. Organic materials including both polymers and small molecules have been used to fabricate LEDs. LEDs fabricated from these materials offer several advantages over other technologies, such as simpler manufacturing, low operating voltages, and the possibility of producing large area and full-color displays. Organic polymers generally offer significant processing advantages over small molecules especially for large area EL display because polymer films can be easily produced by casting from solution.
Conjugated polymers are a class of polymers that possess an extended xcfx80-bond network along polymer main chain. Their electronic states can delocalize caused by the effect of the electron-lattice and electronxe2x80x94electron interactions. Conjugated polymers such as poly(phenylvinylene) (PPV) were first introduced as EL materials by Burroughes et al. in 1990 (Burroughes, J. H. Nature 1990, 347, 539-41). To improve the polymer solubility, dialkoxy-substituted PPV such as poly(2,5-dialkoxy-p-phenylenevinylene) and MEH-PPV, poly[2-methoxy-5-(2xe2x80x2-ethyl-hexoxyl)-p-phenylenevinylene] have been developed. EL efficiency has been improved by balanced electron-hole injection and recombination of the charge carriers. Other conjugated polymers such as polydialkylfluorene (PF) (Ohmori, Y. et al Jpn. J. Appl. Phys. Part 2 1991, 20, L1941-L1943), poly(p-phenylene) (PPP) (Grem, G. et al Adv. Mater. 1992, 4, 36-7), and poly(thiophene) (Ohmori, Y. et al Solid State Commun. 1991, 80, 605) have also been studied.
The light-emitting layer of an EL device comprises a highly luminescent material where electroluminescence is produced as a result of electron-hole pair recombination in this region. In order to achieve efficient light output the efficient and highly fluorescent materials are required. 9,10-Diaryl substituted anthracenes are well known for their high fluorescence efficiency. The highly efficient light output and high operational stability of EL devices have been disclosed in commonly assigned U.S. Pat. Nos. 5,935,721 and 5,972,247 by using substituted anthracenes as light-emitting materials.
It is an object of the present invention to provide luminescent polymeric materials useful for polymer EL devices.
It is a further object of the present invention to provide various energy bandgap luminescent polymers which emit broad range of color.
A new class of anthracene-based polymers has been discovered for use in electroluminescent devices.
These objects are achieved in an electroluminescent device comprises an anode, a cathode, and an emissive layer having a polymer luminescent material disposed between the anode and cathode, the polymer luminescent material includes diarylanthracene-based conjugated polymer having a repeating unit of the following formula: 
wherein:
Ar1, Ar2, and Ar are each individually aryl or substituted aryl of from 6 to 40 carbon atoms; or
Ar1, Ar2, and Ar are each individually substituted heteroaryl or unsubstituted heteroaryl having 4 to 40 carbons.
The present invention provides light-emitting materials with a number of advantages that include good solubility, efficiency and stability. The emitting color of the polymer can be easily tuned by the incorporation of desired Ar group. Furthermore, other electro-optical properties can also be tuned with Ar group. The materials from the present invention can also be used as host materials for other light emitting materials.